Thread: making headers

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here's the start I got so far

Loooooks Good.

Originally posted by tcodi
here's the start I got so far

thats a good start.

better than i could do good job.....i give you a "a"

Looks great to me, but you might want to consider moving the brake lines to the inside of the frame or at least putting a heat shield over them

Exit out the fenderwell?

looks good, I like the attention to detail, esspecially cleaning up the pipes around the cut so it doesn't get any weld contamination.

I have been following this thread for a while now, and I just want to ask a question, are all the primary pipe lengths going to be as close as possible to the same length, and how much importance do you attach to that ?

I dont want to hijack your thread, but I just may save you a lot of work.

Thats going to be a nice truck.

well, my headers got put on hold for a little because like an idiot I ordered the wrong diameter pipe when I ordered my mandrel bends, the new ones should come today though.
As for equal length tubes, I'm gonna try as best I can to get them all equal length, it's gonna be tough though. Those tubes on the rear cylinders are gonna be a heck of a lot shorter, I may have to take them on a full 360 degree wrap around to eat up length.
I think it's pretty important, if your gonna have headers and get the advantage of tuning for the return of pressure waves, you may as well set it up so that they all contribute in the same rpm range.
Hopefully in another two days or so I'll have some pictures.

I am gonna do some sort of heat sheild for the brake lines, I set up those lines before I planned on going outside the frame with the headers.

You have a BBC right ?, just checking as I want to get the firing order as pertains to headers. I have some tests on headers that may surprise you.

Right here is a condensed version of an interesting article as pertains to street headers.

Worrying about equal primary lenghts is a waste of effort, in practice a 2 plane cranked V8 engine such as the chevy is insensitive to quite substantial primary lenght changes. 4 cylinder engines respond well to equal primary length. But a chevy V8 is'nt 2 inlone 4's joined together to form a V8. It is 2 seperate V4's. The exhaust pulses are spaced at 90 -180 -270 -180 -90 and so on. The discharge of 2 cylinders only 90 degrees apart appears at the collecter as 1 large cylinder. This means the primarys act like they are on a 4 cylinder engine, but the collectors acts as if it were on a 3 cylinder engine having different sized cylinders turning at few revs. Life sure is complicated aint it ?

Since the typical street header can have primary pipes ranging from 24 to 36 inches in length. Each pipe comes into it's own flow range in the engines usable power range. Thus this therefore broadens the powerband of the engine making it ideal for street applications. So put simply equal length appear to only work on highly tuned racing engines with a very narrow powerband.

Collector length is whats important on the street a small diameter long coollector boosts bottom end torque, and you can feel that in a street engine.

Hope this helps in your fabricating decision. S

well that's good news for me. that will save me a heck of a lot of work trying to get those things equal.
As a matter of fact, the full headers that I cut apart to get started did not have equal length tubes either. The fronts were a good 12" longer than the rears.
thanks for the info.
Hopefully when I get home tonight I'll have a box from summit on my doorstep to keep me busy for a few days.

Southerner, do you recall what is the effect of the header pipe after the header. My impression is that it is better to have a 2 1/2" collecter diameter rather than a 2 1/4" tubing, but you mention torque enhancement with a smaller collecter and I would like low rpm torque to run in OD at about 1800 rpm.

Don Shillady
Retired Scientist/teen rodder

yep,... what you say is right Don, you run a smaller diameter collector, but it is also longer so that it keeps the exhaust gas velocity up at the lower rpms. This is crucial so that the fast moving gases create a low pressure reading in the cylinder.

Also I might add the most appropriate way to keep exhaust gas velocity up is to get your exhaust as free flowing as possible. This is achievable with the right mufflers, resonator boxes and correct diameter tubing. You would need a muffler that flows 2.2 cfm per horsepower to achieve no or low flow restriction.

This is a thing that surprises me, we all do the high performance mods on our engines, all the large flowing carbs, manifolds, heads, cams and headers. Everything ends at the header flange and either a stock exhaust or a poorly thought out one ends up connected to the collector pipes and we wonder why this thing feels clogged up ?

Originally posted by southerner
yep,... what you say is right Don, you run a smaller diameter collector, but it is also longer so that it keeps the exhaust gas velocity up at the lower rpms. This is crucial so that the fast moving gases create a low pressure reading in the cylinder.

Also I might add the most appropriate way to keep exhaust gas velocity up is to get your exhaust as free flowing as possible. This is achievable with the right mufflers, resonator boxes and correct diameter tubing. You would need a muffler that flows 2.2 cfm per horsepower to achieve no or low flow restriction.

This is a thing that surprises me, we all do the high performance mods on our engines, all the large flowing carbs, manifolds, heads, cams and headers. Everything ends at the header flange and either a stock exhaust or a poorly thought out one ends up connected to the collector pipes and we wonder why this thing feels clogged up ?

i think if you are looking for bottom end you need the small exhaust. big exhaust will hurt you on bottom end i think. big exhaust on top end. JMO

Originally posted by DennyW
You mean like this Southerner?

on the st. 3" will kill you.